JPS5949035B2 - Cutter device for sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sewing machine that successively sews a large number of work cloths, and particularly to a sewing machine that continuously sews a large number of work cloths.
The present invention relates to a cutter device that sucks with a suction means and automatically cuts with a cutter.

In general, in a sewing machine equipped with this type of cutter device, in the case of normal sewing in which the entire length of the side edge of a given workpiece cloth is sewn, a detector placed near the seam forming means detects the front edge of the workpiece cloth. The edge and the trailing edge are detected, and after a predetermined period of time has elapsed based on the output signal, a cutter placed on the cloth feed side from the detector is activated to cut the yarn connected to the front edge and the trailing edge of the work cloth. The chain is cut at a predetermined distance from the ends of the cloth, and the cut chain is removed from a suction port of a suction means disposed near the cutter.

However, in the case of intermediate stitching in which the sewing machine performs sewing from the middle of the side edge of the work cloth, the non-sewn edge has already been fed to the cutting position of the cutter when sewing starts, so it is not possible to sew as in the case of normal stitching. If the cutter is operated after a predetermined period of time has elapsed, there is a risk that the non-sewn edge may be accidentally cut.

Therefore, in such cases, sewing work is currently performed without cutting the cutter based on the detector. The chain will not be cut, and the processed cloth will be transferred by the cloth feeding means consisting of the feeding teeth, the cloth presser, etc. while the chain is being sucked into the suction port of the suction means. There was a risk that the feeding operation would be hindered.

The present invention has been made to solve the above-mentioned problems, and includes a sewing machine equipped with cloth feeding means for feeding the work cloth in one direction in the vicinity of the seam forming means. a suction means disposed on the cloth feeding side of the means for suctioning the thread chain formed by the stitch forming means; and a suction means disposed near the suction port of the suction means for cutting the suctioned thread chain. a cutter, an actuating means for the cutter, and a plurality of cutters disposed on the cloth feeding side of the cutter and away from the cutter in a direction orthogonal to the cloth feeding direction, and for detecting the presence or absence of a work cloth. a detector; and when the work cloth is fed from the cloth feeding direction and the front edge and rear edge of the work cloth are detected by the detector, a first actuator for activating the actuating means after a predetermined time has elapsed, respectively. control system and
By providing a second control system for immediately activating the actuating means when the work cloth is fed from a direction perpendicular to the cloth feeding direction and the feeding state is detected by the detector, the work cloth In the case of normal sewing in which the material is fed from the cloth feeding direction, the front edge and the rear edge of the workpiece cloth are sequentially detected by the detector, and the cutter is operated after a predetermined time has elapsed, and the front and rear edges are detected by the detector. It is possible to reliably cut the thread chain connected to the edge, and in the case of intermediate stitching where the workpiece cloth is fed from a direction perpendicular to the cloth feeding direction, the feed state is detected by the detector and the cutter is immediately activated. When activated, it is possible to quickly cut the chain of threads that are connected in the middle of the side edges of the work cloth and are being sucked into the suction means, thereby eliminating the risk of cutting the side edges of the work cloth.
It is an object of the present invention to provide a cutter device for a new sewing machine that can reliably prevent the fear of interfering with the feeding operation of workpiece cloth.

Below, the configuration of an automatic overlock sewing machine embodying the present invention will be explained with reference to the drawings. In the drawing, 1 is a sewing machine head fixed to a cloth board 2 of an overlock sewing machine (hereinafter referred to as sewing machine) M, and 3 is a needle. A stitch forming mechanism is configured in cooperation with a looper (not shown), and an overlock stitch is formed on the work cloth K.

Reference numeral 4 denotes a needle plate having a needle hole through which the needle 3 passes, and a feed dog 5 that makes four known movements moves in and out.

Reference numeral 6 denotes a presser foot, which cooperates with the feed dog 5 to transport the workpiece cloth K in the direction of the arrow X.

C is a cutter composed of a lower blade 7 embedded in the cloth plate 2 on the feeding side from the drop point of the needle 3, and an upper blade 8 that rotates perpendicularly to the blade surface of the lower blade 7, During sewing, the thread chain L or tape, etc. connected to the front and rear edges of the workpiece cloth is cut.

This chain L is driven by the sewing machine M, and the needle 3 is moved as shown in FIG. 2 immediately before and after sewing the work cloth K.
By the operation of the upper and lower loopers, the tongue piece 6a of the presser foot 6
It is formed so as to wrap around the tongue of the throat plate 4, and is sent toward the cutter 〇.

Therefore, in the case of normal sewing, this chain L will be connected to the front and rear edges of the workpiece cloth as shown in Figure 3A, and in the case of intermediate sewing, as shown in Figure 3B. In this way, the chain L is connected to the middle of the side edge and the rear edge of the work cloth.

Reference numeral 10 denotes a chain suction pipe which is disposed adjacent to the upper blade 8 and extends in the cloth feeding direction, and which is connected to a means (not shown) for generating negative pressure such as a blower. A chain suction hole 10a is formed near the upper blade 8, as shown in FIG.

Therefore, the chain L, tape, etc. connected to the front and rear edges of the work cloth cut by the cutter C are sucked in through the chain suction hole 10a and removed.

Reference numeral 11 denotes an electromagnetic drive body fixed to the back surface of the sewing machine head 1 to operate the cutter C, and 12 is an operating rod of the electromagnetic drive body, the lower end of which is connected to a shaft 14 as shown in FIG. It is pivotally connected to the lever 13.

15 connects its base end to the other end of the lever 13 and the fixing screw 1.
6, and the chain suction pipe 10
It is pivotally supported by a support member 17 disposed on the back surface of the cutter, and its tip is fixed to the base end of the upper blade 8 of the cutter 〇.

Accordingly, the vertical movement of the operating rod 12 of the electromagnetic drive body 11 rotates the rotating shaft 15 via the lever 13, and the upper blade 8 is rotated to perform a cutting operation.

Reference numeral 20 denotes a cloth detection device for detecting the transferred work cloth K from above the cloth plate 2, and is arranged on the cloth feeding side of the cutter C and away from the cutter C in a direction orthogonal to the cloth feeding direction. The first photosensor 21 and the second
As shown in FIG. 5, the second photosensor 22 is located near the drop point of the needle 3 (in this embodiment, the workpiece cloth is located at a position 35 mm away from the drop point toward the feed side as a reference). K) and the first
The photo sensor 21 is placed at a certain distance from the second photo sensor 22 on the feed direction line (75 mm in this embodiment).
) on the cloth feeding side.

Both sensors 21 and 22 are composed of a light emitting element such as a light emitting diode and a light receiving element such as a phototransistor.
The light from the upper light emitting element is detected by the light receiving element via a reflection plate (not shown) embedded in the cloth plate 2, and the work cloth K blocks the light to detect the cloth. I am doing it.

In this embodiment, a detection signal is generated which is at a high level (high potential) when the light is blocked by the work cloth K, and at a low level (0 potential) when the light is not blocked.

Next, a control circuit for operating the cutter device configured as described above in conjunction with the sewing machine M will be explained based on FIGS. 6 and 7.

FIG. 6 shows the entire control circuit, which can be broadly divided into a first timing setting control circuit 30 that sets the operation timing of the cutter device in the case of normal sewing on a workpiece cloth;
, a second timing setting control circuit 3 that sets the operation timing of the cutter device in the case of halfway sewing on a workpiece cloth;
1. The first and second timing setting control circuits 30 and 31
, and an operation control circuit 33 that controls the operation of the operation circuit 32, and is built in a control box fixed to the leg of the sewing machine M. has been done.

First, the first timing setting control circuit 30 will be explained. 35 is a NAND circuit, and after a certain period of time when the cloth detection signal C15W (see FIG. 7C) of the first photosensor 21 is generated The sewing machine drive signal MC (see FIG. 7C) generated when the sewing machine M is driven after the cloth is detected by the photosensor 21, and there is a time delay during that time.
Cloth detection signal c2SW(
(see Figure 7C) is input, and the output signal shown in Figure 7 is output.

Reference numeral 36 denotes a monostable multivibrator that operates by capturing the falling edge of the leading edge of the output signal of the NAND circuit 35, and operates the upper blade 8 of the cutter C in response to the cloth detection signal c2SW and the sewing machine drive signal MC. In the case of normal sewing, after the front edge of the work cloth that is transferred to the feed side at a constant speed passes between the second photosensor 22 and the reflective plate, the front edge is the cutting position of the cutter C. The timing of the output waveform from the output terminal Q is adjusted by the pulse width T shown in FIG. 7E so that the chain L extending in front of the front edge is cut before reaching the front edge.

This pulse width T1 is adjusted by a resistor 37 and a capacitor 38 that determine the time constant of the monostable multivibrator 36, and is set to T1=3Qmsec in this embodiment.

39 is a monostable multivibrator that operates by capturing the rising edge of the output signal of the NAND circuit 35, and similarly to the above, it determines the operation timing of the upper blade 8 in response to the two signals C2C25W5. The work cloth K is released from the feeding means such as the feeding dog 5 and is moved to an air feeding device etc. (
(not shown), the output waveform from the output terminal Q is changed so that the chain L is slowly transferred to the delivery side by the chain L (not shown), and after the trailing edge completely passes the cutting position of the cutter C, the trailing edge cuts the chain L that continues behind the trailing edge. The pulse width T2 shown in FIG. 7F
The timing is adjusted.

This pulse width T2 is adjusted by a resistor 40 and a capacitor 41 that determine the time constant of the monostable multivibrator 39, and is set to T2=lQQmsec in this embodiment.

42 connects each input terminal to each monostable multivibrator 3
6.39 is a NOR circuit connected to the output terminal Q,
The output signal from this output terminal exhibits the output waveform shown in FIG. 7G depending on the input signal from each monostable multivibrator 36, 39, and is input to the next stage operating circuit 32.

Next, the second timing setting control circuit 31 will be explained.

43 is a NAND circuit, and the first photosensor 2
1 cloth detection signal C15W and cloth detection signal C25W from the second photosensor 22 are input.

Therefore, as shown in FIG. 5, in the case of intermediate sewing in which the work cloth K is fed in from a direction perpendicular to the cloth feeding direction (Y arrow direction), the first photosensor 21 and the second photosensor 22 are activated at the same time. The side edges of the processed cloth will be detected,
The cloth detection signal Cl5W is shown in FIG. 7H as the cloth detection signal (c2S
W) has an output waveform as shown in Figure 7I, so the same N
The output of the AND circuit 43 shows the output waveform shown in FIG. 7J.

Note that in this case, the sewing machine drive signal MC is generated, as shown in FIG. 7H, a certain period of time after the generation of the cloth detection signal C15W in FIG. 7H, as described above.

Reference numeral 44 denotes an AND circuit having one input terminal connected to the output terminal of the NAND AND circuit via a NOT circuit 45, and a sewing machine driving signal MC being inputted to the other input terminal via the NOT circuit 45.

Therefore, by inputting the drive signal MC shown in FIG. 7H and the output signal of the NAND circuit 43 shown in FIG. 7J, the output waveform shown in FIG. 7 is generated.

46 is a waveform shaping circuit composed of a differentiator circuit and a rectifier circuit, which captures the leading edge rising and trailing edge falling of the output signal shown in the seventh diagram of the AND circuit 44 in the previous stage, and generates positive and negative trigger pulses. Only the positive trigger pulse generated by catching the rising edge of the leading edge is taken out by the rectifier circuit as shown in FIG.

Note that in this embodiment, the pulse width T3 of the trigger pulse is 2μ.
The differential circuit of the waveform shaping circuit 46 is used to adjust and set the waveform shaping circuit 46 so that the difference is sec.

Next, the operating circuit 32 will be explained.

47 is a monostable multivibrator that operates by inputting the outputs from the first timing setting control circuit 30 and the second timing setting control circuit 31, and its output terminal Q
The output signal of the NOR circuit 42 (the seventh
When the output signal (see Fig. M) is inputted, the output waveform of the pulse width T4 shown in Fig. 7H is shown by capturing the trailing edge rise, and the output signal of the waveform shaping circuit 46 (see Fig. 7
(see) is input, the falling edge of the trigger pulse is captured and the output waveform of pulse width T4 in FIG. 7O is shown.

This pulse width T4 is adjusted by a resistor 48 and a capacitor 49 that determine the time constant of the monostable multivibrator 47.

Note that the sum of the pulse width T4 and the pulse width T1 of the monostable multi-bi break 36, which is the time T1+T4, is the second
This pulse width T4 is adjusted and set together with the pulse width T1 so that the time required for transferring the work cloth from the detection position of the photosensor 22 to the cutter C position is the same as or shorter than that.

50 is an AND circuit in which one input terminal is connected to the output terminal of the monostable multivibrator 47 via a NOT circuit 51, and the other input terminal is connected to the output terminal of the operation control circuit 33 via a NOT circuit 51. The base terminal of a switching transistor 52 whose emitter is grounded is connected to its output terminal.

The AND circuit 50 inputs the output of the monostable multivibrator 47 to the next stage transistor 52 based on the output signal of the operation control circuit 33.

Reference numeral 53 denotes an electromagnetic coil connected to the collector terminal of the transistor 52, which actuates the operating rod 12 built into the electromagnetic driver 11.

Therefore, the transistor 52 operates based on the output signal of the AND circuit 50, and the electromagnetic coil 53 is energized to cause the cutter 〇 to perform a cutting operation.

Next, the operation control circuit 33 will be explained.

54 is a detection signal C15 from the first photosensor 21
This is a monostable multivibrator that operates by capturing the rising edge of the leading edge of W, and the pulse width T5 shown in FIG.
generates a pulse signal.

This pulse width T5 is made to match the time width from generation of the cloth detection signal Cl5W to generation of the sewing machine drive signal MC.

Therefore, for the cloth detection signal C15W shown in FIG. 7A, the output signal shown by the dashed line P2 in FIG. 7, and for the cloth detection signal C15W shown in FIG. 7H, the output signal shown in FIG. It will be generated from the output terminal Q.

57 is the monostable multivibrator 54 in the previous stage, Fig. 7 P
This is a monostable multivibrator that operates by capturing the rising edge of the output signal shown in FIG. 7, and outputs from its output terminal Q a pulse signal having a pulse width T6 shown in FIG.

This pulse width T6 is normal, and is longer than the time required for the second photosensor 22 to detect the leading edge of the workpiece cloth after the workpiece cloth K is transferred from the feed side and the sewing machine drive signal MC is generated. is also set to be shorter.

60 is a NAND AND circuit with one input terminal connected to the output terminal Q of the monostable multivibrator 57 in the previous stage.
The detection signal c2SW from the second photosensor 22 is input to the other input terminal.

FF is a flip-flop whose set side input terminal is connected to the NANDAND circuit output terminal, and whose other reset side input terminal is connected to the second photosensor 22.
Detection signal C25W from is input.

In this flip 70-tube FF, the output on the set side is normally at a low level, and the output on the reset side is at a bi level.

As a result, when a low level output is input from the NAND circuit 60 in the previous stage, the set side output terminal is inverted from low level to by level, while the reset side output terminal is inverted from by level to low level, and the reset side output The signal is inputted to the AND circuit of the operating circuit 32 at the next stage.

The output of the AND circuit 50 at the next stage is such that in the case of normal sewing, an output waveform as shown in FIG. 7 R1 and as shown in FIG. 7 S in the case of intermediate sewing is generated in one sewing operation.

Next, the operation of the control circuit configured as described above will be explained.

Now, when forming a normal seam on the edge of the work cloth, the first photosensor 21 first detects the passage of the front edge of the work cloth, and as shown in FIG. The output signal rises from the low level to the by level, and based on its detection, the sewing machine M is driven by generation of the sewing machine drive signal MC (see FIG. 7C) after a certain period of time.

As a result, edge stitching is performed on the work cloth while being transferred by the feed dog 5, etc., and eventually the second photosensor 22 detects the front edge of the work cloth, and the detection signal c2SW (seventh
(see Figure C).

Then, due to the generation of the sewing machine drive signal MC and the detection signal C25W, the output of the NAND circuit 35 falls from the by level to the low level (see Figure 7), and this fall causes the monostable multivibrator 36 to operate, and the NO
The next stage monostable multivibrator 4 is connected via the R circuit 42.
Operate 7.

Therefore, this monostable multivibrator 47 operates after T1 hours after the detection signal c2SW is generated, and sends an output signal (see N in FIG. 7) held for 14 hours to the AND circuit 50 in the next stage.
It is input via the T circuit 51.

At this time, the NAND circuit 60 of the operation control circuit 33 maintains a bi-level output based on the detection signal c2SW shown in FIG. 7C and the output signal shown in the dashed line Q2 in FIG. First, the signal is held at a low level and is input to the other input terminal of the AND circuit.

As a result, the AND circuit 50 generates the output signal shown in FIG. 7R based on the output signal of the monostable multivibrator 47, operates the transistor 52, and excites the electromagnetic coil 53.

Therefore, after the second photosensor 22 detects the workpiece cloth K, the cutter 〇 is not operated immediately, and the front edge of the workpiece cloth is transferred immediately before the cutter C by the feed dog 5 etc. for a time T1. Later, the cutter C is operated, and the chain L extending forward from the front edge is cut at a good timing leaving a certain length from the front edge, and after 14 hours, the cutter C retreats so as not to interfere with the transfer to the work cloth.

The cut chain L is then sucked into the chain suction pipe 10 and removed.

After the cutting operation of the chain L connected to the front edge is completed, the work cloth is sewn and sequentially transferred to the delivery side, and the second photosensor 22 detects the passage of the rear edge of the work cloth. Then, the detection signal C25W falls as shown in FIG. 7C.

As a result, the output of the NAND circuit 35 rises, and the monostable multivibrator 39 in the next stage operates, and the monostable multivibrator 47 is output via the NOR circuit 42 as before.
make it work.

Based on the operation of the monostable multivibrator 47, the transistor 52 is operated via the AND circuit 50 to excite the electromagnetic coil 53.

Therefore, after the second photosensor 22 detects the passage of the trailing edge of the workpiece cloth, the cutter C is immediately activated, and the trailing edge of the workpiece cloth is moved by the air feeding device or the like to the position of the cutter C. Twelve hours after passing, the cutter C is activated, and the chain L connected to the trailing edge is cut in a timely manner leaving a certain length from the trailing edge, and 14 hours later, the cutter C retreats and begins the next cutting operation. Be prepared.

During the above-mentioned operation period during normal sewing, the output of the AND circuit 44 of the second timing setting control circuit 31 corresponds to each input signal C15W, C2C25 shown in FIG. 7A, B, and C.
Since it is always at a low level due to W9, a trigger pulse from the waveform shaping circuit 46 at the next stage is not generated, and the monostable multivibrator 47 is not operated.

Next, a case will be described in which a seam is formed by halfway stitching the edge of a workpiece cloth.

Now, when the work cloth K is fed in the Y direction as shown in FIG. 5, the first and second photosensors 21.
22 simultaneously detects the edge of the workpiece cloth and generates detection signals C15W and C25W shown in FIG. 7H and (2), respectively.

As a result, the NAN of the second timing setting control circuit 31
The output of the D circuit 43 (see FIG. 7M) immediately falls from high level to low level and is input to the AND circuit 44 at the next stage.

At this time, since the sewing machine drive signal MC has not yet been generated, the output of this AND circuit 44 (see Figure 7) simultaneously rises from low level to high level, and then the sewing machine drive signal MC (see Figure 7) is generated. The signal falls to a low level.

Then, catching the rising edge of the output waveform of the AND circuit 44, the next stage waveform shaping circuit 46 generates a positive trigger with a pulse width T3 at the same time as the detection signals C15W and c2SW of the first and second photosensors 21.22 are generated. Pulse (Fig. 7 M
), and the next stage monostable multivibrator 47
input to input terminal A of.

Therefore, this monostable multivibrator 47 detects the fall of this trigger pulse and operates immediately, and the next stage A
It is input to the ND circuit 50.

At this time, since the monostable multivibrator 57 of the operation control circuit 33 operates simultaneously with the generation of the sewing machine drive signal MC, the set side output terminal of the flip-flop FF is still at a low level, and the other input of the AND circuit 50 A high level output is input to the terminal via the NOT circuit 51, and the transistor 52 is operated with the output shown in FIG. 7S, and the electromagnetic coil 53 is immediately excited.

As a result, the electromagnetic coil 53 outputs detection signals C15W and C25.
After W generation T3 time 2μSeC, it is excited and held for 14 hours.

At this time, in the first timing setting control circuit 30, the monostable multivibrator 36 operates at the same time as the sewing machine drive signal MC is generated, but the flip-flop FF of the operation control circuit 33 has already been inverted by the operation of the monostable multivibrator 57. Therefore, the AND circuit 50 does not generate the operational output of the transistor 50 based on the monostable multivibrator 36 of the first timing setting control circuit 30.

Therefore, the cutter 〇 is operated immediately before the non-sewn edge of the work cloth to be partially sewn is fed into the cutter 〇 installation position, and the cutter 〇 is operated without cutting the end edge of the work cloth as shown in Fig. 2. Cut the chain L shown in .

The cut chain L is then sucked into the chain suction pipe 10 and removed.

After the cutting operation of the chain L is completed, the work cloth is sewn and sequentially transferred to the delivery side, and when the second photosensor 22 detects passage of the trailing edge of the work cloth, the The reset side input terminal of the flip-flop FF of the operation control circuit 33 receives a low level input signal, and the set side output terminal is inverted from high level to low level.

As a result, the transistor 52 operates based on the operating output of the monostable multivibrator 39 of the first timing setting control circuit 30, and the electromagnetic coil 53 is excited, as in the case of normal sewing.

Therefore, similarly to the normal sewing described above, the trailing edge of the workpiece fabric passes through the position of the cutter C by the air feed device, etc.
Two hours later, the cutter C is activated, and the chain L connected to the rear edge is cut at a good timing leaving a certain length from the rear edge, in preparation for the next cutting operation.

As described in detail above, the present invention provides a sewing machine equipped with a cloth feeding means for feeding a workpiece cloth in one direction near a seam forming means, which is disposed on the cloth feeding side with respect to the seam forming means, A suction means for suctioning the thread chain formed by the forming means, a cutter disposed near the suction port of the suction means for cutting the thread chain being sucked in, and an actuating means for the cutter. and disposed on the cloth feeding side of the cutter and away from the cutter in a direction orthogonal to the cloth feeding direction,
A plurality of detectors are provided to detect the presence or absence of a work cloth, and a predetermined time period elapses when the work cloth is fed from the cloth feeding direction and the front and rear edges of the work cloth are detected by the detectors. a first for later actuating said actuating means;
and a second control system for immediately operating the actuating means when the work cloth is fed from a direction perpendicular to the cloth feeding direction and the feeding state is detected by the detector. Therefore, in the case of normal sewing in which the work cloth is fed from the cloth feeding direction, the front edge and the rear edge of the work cloth are sequentially detected by the detector, and the cutter is operated after a predetermined time has elapsed, and the cutter is operated. It is possible to reliably cut the chain of threads connected to the front and rear edges.
In addition, in the case of halfway sewing where the work cloth is sewn from a direction perpendicular to the cloth feeding direction, the feed state is detected by the detector and the cutter is activated immediately, so that the cutter is continuously sewn in the middle of the side edge of the work cloth. A cutter device that can quickly cut the thread chain sucked into the means and reliably prevent the risk of cutting the side edges of the work cloth or interfering with the feeding operation of the work cloth. It has excellent industrial effects.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway front view showing the overall configuration of an overlock sewing machine illustrating an embodiment of the present invention, Fig. 2 is an enlarged plan view of the main parts of the sewing part of the overlock sewing machine, and Fig. 3A , B is an explanatory diagram illustrating the state in which the chain is connected to the work cloth, FIG. 4 is an enlarged perspective view of the main parts of the cutter device, FIG. 5 is a plan view of the overlock sewing machine, and FIG. 6 is a control circuit diagram of the cutter device. , FIG. 7A-8 is a diagram of each output waveform of the control circuit. Sewing machine head 1, needle 3, lower blade 7, upper blade 8, electromagnetic drive body 11
, the first photosensor 21, the second photosensor 22, the first
Timing setting control circuit 30, second timing setting control circuit 31. Operation circuit 32, operation control circuit 33, overlock sewing machine M, cutter C, chain, zero on work cloth

Claims (1)

[Scope of Claims] 1. In a sewing machine equipped with cloth feeding means for feeding the work cloth in one direction in the vicinity of the seam forming means, the seam forming means is disposed on the cloth feeding side with respect to the seam forming means. a suction means for suctioning the yarn chain formed by the suction means; a cutter disposed near the suction port of the suction means for cutting the suctioned yarn chain; and an actuating means for the cutter; a plurality of detectors disposed on the cloth feeding side of the cutter and away from the cutter in a direction orthogonal to the cloth feeding direction, for detecting the presence or absence of a work cloth; , a first control system for activating the actuating means after a predetermined time has elapsed when the front end edge and the trailing end edge of the work cloth are detected by the detector; a second control system for immediately activating the actuating means when the supply state is detected by the detector.